Terminal blocks form electrical connections between a set of leads and an electrical body having an array of contacts. The terminal block includes a terminal housing, receptacles in the housing to receive the leads, and electrical conductors extending from the receptacles out of the housing. The exposed conductors are arranged to engage the contacts of the electrical body.
Modular terminal blocks have the terminal housing formed from a module stack made of a number of like slices or housing modules. Each module contains a set of receptacles and a set of conductors. The modules are placed or stacked side-by-side, with end plates closing the ends of the module stack to form the terminal housing.
The electrical body, which may be a printed circuit board, is connected to the conductors of the module stack. The conductors extend through plated contact holes or vias in the circuit board to electrically interconnect the receptacles with the circuit board.
The widths of the housing modules making up a module stack vary due to manufacturing tolerances. As a result, the overall length of the module stack and the positioning of the modules in the stack will also vary among different module stacks that are intended to connect with the same type of circuit board. The module stack may be made up of a relatively large number of housing modules, and tolerance buildup along the stack may cause misalignment of the conductors. The positions of the conductors may not accurately correspond or align with the predetermined arrangement of vias on the circuit board.
The circuit board is placed above the module stack with the vias positioned above the corresponding conductors. As module stacks are getting longer and longer, manufacturing tolerances may result in some conductors not accurately aligned with the vias in the circuit board. The misaligned conductors may be damaged during insertion or may even prevent the circuit board from being installed.
The circuit board is moved toward the module stack, with the conductors entering the vias of the circuit board. The conductors and vias are sized to generate a press fit that electrically connects the conductors with the circuit board.
The press fits generated between the conductors and the circuit board applies forces on the conductors that tend to cause the conductors to bend or deflect in the housings. As the module stacks get longer and the number of conductors increase, the deflection of the conductors makes it even more difficult to maintain proper conductor alignment during installation. Conductors may be damaged or insertion forces may exceed acceptable levels.
Terminal housings include covers that close to cover the conductors and the contact portion of the circuit board. The cover is held closed by the end plates attached to the module stack after the circuit board is installed on the conductors. As the module stacks get longer, however, the cover has a tendency to bow upward between the end plates and expose the contacts.
Thus there is a need for a modular terminal block having an improved modular terminal housing. The improved terminal housing should assure accurate alignment of the conductors with the vias despite manufacturing tolerance buildup along the module stack. The conductors should be better supported in the housing modules to resist deflection of the conductors during attachment of the circuit board. The terminal housing cover should remain closed along its entire length after the circuit board is attached to the module stack.